1. Field of the Invention
The present invention relates to an apparatus for measuring a distance between components of an examinee's eye.
2. Description of Related Art
Conventionally, there is known an apparatus for measuring a distance between components of an examinee's eye (e.g., an ocular axial length, a depth of an anterior chamber of an examinee's eye) that includes a projection optical system arranged to project low coherent light emitted from a light source onto two sections (components) of the examinee's eye that are located at different positions in an axial direction of the eye, and a photo-receiving optical system arranged to photo-receive reflection light from the two sections as interference light by a photodetector, the apparatus being arranged to move an optical-path-length varying optical member in an optical axis direction, that is a member capable of adjusting an optical path difference between first light and second light that are made by dividing the low coherent light by a beam splitter, and measure the distance between the components based on a travel position of the optical-path-length varying optical member at the time when the photodetector detects the interference light (see Japanese Patent Publication Laid-Open No. Hei02-297332).
In the case of the above-described conventional apparatus, when a trigger signal for starting measurement is output, the optical-path-length varying optical member is moved from its original position toward a predetermined direction, and when optical path lengths of the first light and the second light agree with each other, an interference signal is output from the photodetector. Then, the measurement is made based on the travel position of the optical-path-length varying optical member at the time when the interference signal is detected. It is to be noted that after reaching its travel-limiting position, the optical-path-length varying optical member is moved in the reverse direction to be returned to its original position.
However, because the conventional apparatus has a configuration such that the optical-path-length varying optical member needs to reciprocate two times or more in order to measure the distance two times or more, measurement time is prolonged and a burden is accordingly put onto the examinee.